Do not rewrite sum(Nullable()) to count()

v2: fix for LowCardinality
Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>

src/Analyzer/Passes/NormalizeCountVariantsPass.cpp

@@ -7,6 +7,7 @@
 #include <Analyzer/ConstantNode.h>
 #include <Analyzer/FunctionNode.h>
 #include <Interpreters/Context.h>
+#include <DataTypes/DataTypesNumber.h>
 
 namespace DB
 {
@@ -32,6 +33,11 @@ class NormalizeCountVariantsVisitor : public InDepthQueryTreeVisitorWithContext<
         if (function_node->getArguments().getNodes().size() != 1)
             return;
 
+        /// forbid the optimization if return value of sum() and count() differs:
+        /// count() returns only UInt64 type, while sum() could return Nullable().
+        if (!function_node->getResultType()->equals(DataTypeUInt64()))
+            return;
+
         auto & first_argument = function_node->getArguments().getNodes()[0];
         auto * first_argument_constant_node = first_argument->as<ConstantNode>();
         if (!first_argument_constant_node)

tests/queries/0_stateless/02991_count_rewrite_analyzer.reference

@@ -0,0 +1,4 @@
+Nullable(UInt64)
+UInt64
+Nullable(UInt64)
+UInt64

tests/queries/0_stateless/02991_count_rewrite_analyzer.sql

@@ -0,0 +1,7 @@
+-- Regression test for https://github.com/ClickHouse/ClickHouse/issues/59919
+SET allow_experimental_analyzer=1;
+
+SELECT toTypeName(sum(toNullable('a') IN toNullable('a'))) AS x;
+SELECT toTypeName(count(toNullable('a') IN toNullable('a'))) AS x;
+SELECT toTypeName(sum(toFixedString('a', toLowCardinality(toNullable(1))) IN toFixedString('a', 1))) AS x;
+SELECT toTypeName(count(toFixedString('a', toLowCardinality(toNullable(1))) IN toFixedString('a', 1))) AS x;